The crowds far surpassed the number that turned out for Lincoln even though that premiere involved the most successful director in movie history, Steven Spielberg, and the most decorated in terms of Oscar success, Daniel Day-Lewis.

Last night fans manned every vantage point including the central reservation of O’Connell Street and Cruise, who had a mobile heater trailing after him to keep him warm during a chilly evening, indulged as many of them as he could.

He spent an hour and 20 minutes with fans, much to their delight – and to

the discomfort of the hundreds inside the Savoy Cinemawaiting patiently for the premiere of his new film to start.

Even gardaí trained their camera phones through the thickets of outstretched arms on the 50-year-old star.

“My whole life I have trained. I wanted to do this since I was four years old and I can’t take it for granted," he said when explaining the regime which that goes into his preternatural youthfulness. He doesn't look a day over 30.

“An extraordinary day,” was how he described his dizzying foray which began with a morning visit to the Department of Foreign Affairs. There he was presented with the exhaustive work carried out by the company Eneclann, who researched his family background on behalf of Tourism Ireland.

Cruise’s family history would rival many of his blockbusters. It is a story of selflessness, fortunes lost and found, foreign invaders and a baffling name change – all spanning nearly a millennium of Irish history.

“I knew I was Irish, but I had no idea where it went. I have always been into it [my Irish heritage],” he told reporters having received a certificate of Irish heritage from Tánaiste Eamon Gilmore.

He left clutching a copy of A History of Ireland in 100 Objects, which was originally a series in The Irish Times.

The actor’s full name is Tom Cruise Mapother IV and both the Cruise and Mapother families are from Ireland. The Cruises can trace their presence in Ireland back to the Anglo-Normans and Strongbow. They settled in north Co Dublin.

When her first husband died, Mary Pauline married a second-generation Irishman, Thomas O’Mara. They had a son, Thomas O’Mara jnr. When Thomas snr died, his son took the name Cruise Mapother. He became Tom Cruise Mapother I, Tom Cruise’s great-grandfather. Eneclann.ie believes the name change may be due to the possibility of an inheritance from the Mapother family.

Despite bearing the Mapother name, Tom Cruise is not a blood relative of that family, which will disappoint those in Roscommon who had hoped to welcome him as one of their own.

Patrick Russell-Cruise, the actor’s great-great-great grandfather, returned from the US when he was told his land agent had evicted tenants from lands in Co Westmeath in 1843. He restored the tenants to 500 acres in the townlands of Paristown and Dardistown.